Frontal Hypoperfusion Effects on Antidepressant Outcomes in Late-Life Depression

The long-term goal of this line of research is to determine if in late-life depression (LLD), cerebrovascular dysregulation is predictive of antidepressant outcomes. The investigators hypothesize that vascular pathology resulting in reduced cerebrovascular reactivity contributes to frontocingulate hypoperfusion. Such pathology would impair neurovascular coupling and reduce the ability of the vasculature to improve frontocingulate perfusion during antidepressant treatment. Thus decreased cerebrovascular reactivity and perfusion may be a biomarker of antidepressant nonresponse. As an initial step in this research, the current study will utilize MRI arterial spin labeling (ASL) to examine if cerebrovascular reactivity deficits and resting cerebral blood flow (CBF) deficits predict antidepressant nonremission in LLD. The rationale for this proposal is that it will identify mechanisms by which vascular pathology may contribute to LLD. If the study hypotheses are correct, this crucial next step will support studies examining antidepressant properties of cardiovascular drugs that may reverse vascular pathology and improve perfusion. The investigators will pursue our initial goal by examining ASL predictors of nonremission to a 12-week trial of sertraline. Forty LLD subjects will complete MRI, cognitive testing, and hyperintensity assessment. ASL measured CBF will be obtained during a hypercapnia challenge and at rest with room air. This will help determine if deficits in cerebrovascular reactivity (CVR) and/or resting and on-demand CBF measures predict nonremission. AIM: To test for differences in CVR and CBF in dorsal frontal cognitive control regions between individuals who do and do not remit to a 12-week course of sertraline (defined as MADRS ≤ 7). Hypothesis 1: Compared with remitters, during a hypercapnia challenge nonremitters will exhibit less CVR in the dlPFC and dAC. Hypothesis 2: Compared with remitters, while breathing room air nonremitters will exhibit lower resting CBF in the dorsal anterior cingulate (dAC) and dorsolateral prefrontal cortex (dlPFC). Exploratory Aim: To examine the relationship between ASL measures (CVR to hypercapnia and resting CBF during normoxia) and performance in cognitive domains implicated in LLD treatment outcomes. For this Aim, we will focus on functions involving the dlPFC and dAC, specifically executive function and processing speed. The study will enroll patients from clinical referrals and response to advertisements. In these cases, potential participants will call our study contact number. Study staff will describe the study to them, including a description of the study entry criteria. Those who continue to be interested will then be scheduled for an evaluation. After scheduling, a study physician will review their electronic medical record to assure that potential subjects meet entry criteria. Following policies of the Vanderbilt University Health System Institutional Review Board, written informed consent will be obtained and documented by the study's Research Coordinator before any study-related procedures are performed. The study coordinator will review study procedures and the consent form with each potential participant. Each individual may take as much time as they like to decide if they do or do not wish to participate. There is no randomization. All participants receive open-label sertraline. An initial evaluation will determine eligibility, depression severity, and evaluate medical and psychiatric history. Participants will also complete a detailed battery assessing cognitive function. During this time they will also complete the one-hour MRI session, which includes measurement of cerebral perfusion and vascular reactivity. They will then begin the 12-week trial of open-label sertraline, allowing titration up to the maximum dose of 200mg daily. At the end of the study participants will be referred for ongoing clinical treatment.